Railroad systems include wayside equipment located along the track, such as switches, signals, and vehicle detectors. A wayside equipment may be defined as, for instance, a hot box detector, a hot wheel detector, a dragging equipment detector, a high water detector, a high/wide load detector, an automatic equipment identification system, a highway crossing system, an interlocking controller system, or any other equipment located adjacent the track and used to monitor the status of the track, environment and railway vehicles. Such equipment must necessarily be located throughout the railroad system, and is thus geographically dispersed and often located at places that are difficult to access. Systems are currently in use for communicating operational and status information relating to the condition of the train or the track to control centers. For example, position indicators are provided on switches and right-of-way signals and a signal responsive to the position of a switch is communicated to a control center for that section of track.
Such wayside equipment includes visual wayside signals to provide the driver with right-of-way information not necessarily obtainable by looking down the track. Such equipment is important. Due to the limited field of view from a locomotive and the great inertia of a moving train, it is not always possible to rely on a train operator to stop a train within the range of the driver's vision.
Such wayside signals are subject to normal equipment reliability concerns. The proper operation of such equipment is important to the safe and reliable operation of the railroad. In order to reduce the probability of equipment failures, routine maintenance and inspections are performed on wayside equipment. An inspector will visit the site periodically to inspect the equipment and to confirm its proper operation. Unexpected failures may occur in spite of such efforts, and such failures may remain undetected for a period of time.
U.S. Pat. No. 5,785,283 describes a system and method for communicating operational status of train and track detecting wayside equipment to a locomotive cab. This system is directed to the reduction of radio congestion in the VHF radio system used to communicate between the wayside equipment and the locomotive. This system is described as being used for monitoring or reporting the status of grade crossing warning systems.
FIG. 1 is diagram of a prior art wayside system in which four (4) power lines supply power to signal 1 remote from the controller and four additional power lines supply power to signal 2 remote from the controller. In some installations, the distance between the controller and each signal and the distance between signal 1 and signal 2 may be significant, but limited to several thousand feet. Thus, the reliability of the signals is dependent upon the reliability of the power lines connecting the controller and the signals. In addition, the maximum distance between a controller and signal equipment is limited to the power carrying capability of the power line.
There is a need for upgraded wayside equipment to be more reliable and more easily monitored. There is also a need for upgraded wayside equipment that can be retrofitted to an existing wayside system. Further, there is also a need for an expandable, modular wayside system which can accommodate many controllers, many wayside devices and many control signals without geographic constraints. In addition, such wayside equipment and systems should have failure mode designs which default to safer or more restrictive status in the event of a malfunction or fault.